There are several advantages in using rigid foam insulation in water heater construction and many of these are described in, for example, U.S. Pat. No. 4,861,968 issued on Aug. 29, 1989. It is also advantageous to use expanding foam material that can flow freely within the circumferential space provided within the hot water tank and the outer casing thereof. Foam material, when in its liquid state, is introduced into this space, usually in an envelope or a bag whereby to prevent the foam from attaching itself to the hot water tank, the various controls and pipes therein and the outer wall of the inner casing or the hot water heater. A disadvantage of using bags and envelopes is that it makes it difficult for the foam material to penetrate into small areas and around nipples, controls, and other types of fittings.
In the above-referenced patent there is described an envelope which is formed of opposed sheets of plastic material which is wrapped around the hot water tank surface and wherein predetermined sealed holes are provided in the envelope with the seal formed thereabout whereby to receive therethrough the various components which are secured to the hot water tank and which need to be maintained uncovered or protected from the foam material. Such envelope is therefore time-consuming to install, particularly if the holes are not accurately positioned within the envelope due to an installation error where the top of the envelope may be inverted. Furthermore, with this type of envelope it is difficult to maintain it in position about the hot water tank, as the outer casing is brought down over the outer flexible sheet of the envelope due to the size of the outer sheet which is held loose over the hot water tank. It then becomes time-consuming to readjust the envelope from the open top end of the outer casing and bring the outer sheet over a major section of the outer casing to clamp it with the cover. A still further disadvantage is that these envelopes have to be adapted to specific ones of different types of water heaters where fittings and controls are positioned at different locations and where the inner tank is of different size.
There also exists a need to provide a jacket to contain a liquid foam prior to expansion and distribute the foam in a predetermined controlled manner and wherein the jacket may be adapted to a variety of hot water heaters regardless of the position of couplings, controls or other devices. There is also a need to provide a method of assembly of the jacket on the hot water tank which is simple, efficient and wherein there are no apertures in the jacket to fit around existing controls or other components secured to the hot water tank. There is also a need to provide an insulated hot water heater which is easy to recycle after its useful life.
The majority of water heaters/storage tanks, are currently insulated with foams that use chlorofluorocarbons, normally referred to as CFC's, as blowing agents, for instance, CFC-11 (trichlorofluoromethane) and CFC-12 (dichlorodifluoromethane). These blowing agents have been implicated in the deterioration of the stratospheric ozone layer. A replacement blowing agent known as HCFC's (hydrochlorofluorocarbon's) is currently being used and this agent has been linked to an increase in the global greenhouse effect.
The present invention provides an environmental-friendly water heater which uses `Green Foam` (trade name of Giant Factories) which uses a non-chlorofluorocarbon blowing agent, in this instance, water as a blowing agent. In particular, the intended foam to be used is described in U.S. Pat. No. 5,407,967 assigned to the Stepan Company. This foam is dispensed into an EMB PU-0 machine, and into the water heaters/storage tank circumferential cavities, using a Hi-Tech Mix-head of a straight or L design, (the L head is used when reduced velocity is required). The advantage of using `Green Foam` over the types previously mentioned, is that when the time comes to dispose of the unit at the end of its useful life, the current methods are to dispose of them in an intact condition into overburdened dump sites, or the units are shredded to recycle the raw materials. These procedures create serious problems, as both methods cause the CFC's to be released to the atmosphere, the first gradually, the second instantly. `Green Foam` does not create any of these problems, as any gas released is in the form of carbon dioxide which is what we breath out every time we exhale. It is the intention of the foam insulated water heater of the present invention to allow full re-cycling of all the components used in the manufacturing process.